Protective Wind Shear Barrier Against Hurricanes on Southeast U.S. Coast Likely to Weaken in Coming Decades

This is scary. I have been paying attention for several years, and have seen that most hurricanes in the Atlantic that approach the U.S. are blocked by these conditions.

Dr. Jeff Masters · June 24, 2019, 6:35 AM EDT

It’s well-known that high wind shear—a large change in the wind speed and/or direction with height in the atmosphere—is hostile for hurricane development, since a strong vertical change in winds creates a shearing force that tends to tear a storm apart. For example, even though the Caribbean is warm enough year-round to support hurricanes, we almost never see hurricanes in the winter or spring, since wind shear is very high these times of year due to strong upper-level subtropical jet stream winds.

When low wind shear occurs in summer or fall in the Atlantic’s main development region (MDR), from the coast of Africa through the Caribbean, an active period for major hurricane activity often results. But the major hurricanes that form in the MDR during these situations often have trouble maintaining their intensity when they reach the Southeast U.S. coast, since low wind shear in the MDR is typically accompanied by high wind shear along the Southeast U.S. coast. This high shear, typically associated with strong upper-level winds from the mid-latitude jet stream, helps protect the U.S. East Coast against strikes by full-strength major hurricanes.

But research published last month led by Mingfang Ting of Colombia University, Past and Future Hurricane Intensity Change along the U.S. East Coast, found that the Southeast U.S. protective barrier of high wind shear is likely to weaken in coming decades due to global warming.

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The models showed that this reduced shear signal should start to appear as early as the 2020s or as late as 2050. Not all the news was bad in the study, though—the models also showed a strong increase in wind shear over the Caribbean, and a modest increase over the Gulf of Mexico. These increases in shear would tend to offer more hostile conditions for hurricanes, potentially offsetting the more favorable conditions for increased intensification that warmer ocean temperatures would provide.